1. Field of the Invention
The present invention relates to an image pickup device and an image pickup method that rotate a workpiece having a shape portion containing at least one of a projecting (convex) portion and a recess (concave) portion which is periodically and repetitively formed on the workpiece, and pick up images of the respective shape portions while rotating the workpiece, thereby performing an appearance inspection on the workpiece.
2. Description of the Related Art
There is known an appearance inspecting device for picking up images of a gear as a workpiece fed by a feeding unit and detecting the presence or absence of defects of gear teeth from the pickup images (for example, see JP-A-5-231842). According to this type of appearance inspecting device, a turbine wheel used in a turbocharger for a vehicle engine or the like is freely rotatably supported by a servo motor. The turbine wheel is subjected to step feeding by the servo motor, and the rotation thereof is stopped at an image pickup position, whereby images of all the blades of the turbine wheel can be picked up by a fixedly mounted camera (for example, see JP-A-2009-52917).
It has been desired to pick up images of portions which are periodically and repetitively formed on a workpiece (for example, teeth of a gear, blades of a turbine wheel or the like) and pick up respective images under the same condition (for example, at the same position) when an appearance inspection is executed from the respective pickup images.
However, the appearance inspecting device disclosed in JP-A-2009-52917 has a merit that images of more inspection places can be picked up by rotating the turbine wheel as compared with the appearance inspecting device disclosed in JP-A-5-231842. However, this appearance inspecting device requires a structure and a control operation for stopping a workpiece precisely because the workpiece is step-fed and stopped at a predetermined rotational angle. Furthermore, the turbine wheel is stopped every image pickup and thus much time is required to terminate pickup of all images.